#include <stdio.h>
#include <unistd.h>
int sum(int top){
    int sum = 0;
    for(int i = 0; i <= top; i++)
    {
        sum += i;
    }
    return sum;
}
int main()
{
    int top = 100;
    top = sum(top);
    fprintf(stdout, "sum: %d", top);
    sleep(5);
    printf("\n");
}
